Fluorocarbon aldehydes and their monohydrates



Patented Sept. 18, 1951 FLUOROCARBON mamas AND THEiR MONOHYDRATES DonaldR. Hosted, St. Paul, and Arthur H. Al!!- brecht, White Bear Township,Ramsey County, Minn., assignors to Minnesota Mining & ManufacturingCompany, St. Paul, Minn., a corporation of Delaware No Drawing.Application October 6, 1949, Serial No. 120,008

7 Claim.

The formula for the aldehyde monohydrates (aldehydrols) is R1CH(0H):,and the structural formula is:

11 on In these formulas the symbol R1 represents a non-cyclic(open-chain) saturated fluorocarbon radical (normal or branched)consisting solely of carbon and fluorine, having the formula: CnF2n+LThus the generic formula of our fluorocarbon aldehydes can be writtenas: CnF2n+1CHO, and the formula of the corresponding aldehydrols can bewritten as:

The fluorocarbon aldehydes give a positive Schiii test. They aresensitive to alkalies. They are very sensitive to moisture, forming thecorresponding aldehydrols almost instantaneously in the presence ofwater. They polymerize rapidly at room temperature; more slowly at 30 C.The polymers are claimed in our copending application, S. N. 238,018,filed July 21, 1951.

The aldehydrols are quitestable and can be converted to the aldehydes bydehydration, using a drying agent such as concentrated sulfuric acid orphosphorous pentoxide, etc. For many aldehyde reactions it is notnecessary to convert the aldehydrol to the aldehyde. Thus reactions inthe presence of water can be performed as well by using the aldehydrolas the starting compound, since the aldehyde would in any event beimmediately converted to the aldehydrol upon contact with water. 4

For these reasons it is most expedient to manufacture and sell thealdehydrols, rather than the aldehydes, as the commercial products. Thealdehydrols can be made directly without first making the aldehydes.They can be conveniently supplied in the form of stable high-boilingliquids or solids, as the case may be.

These new compounds are highly reactive despite the presence in themolecule of a saturated fluorocarbon radical. The saturatedfluorocarbons are highly inert and stable. However, the association ofthe fluorocarbon radical with the carbonyl function results in compoundswhich are highly reactive. These compounds possess novel properties asthe result of the carbonyl carbon atom being bonded to a hydrogen-freefluorinatecl carbon atom. These fluorocarbon compounds have a wideapplicability as intermediates for the synthesis of other carboncompounds, providing a means of introducing fluorocarbon radicals intocompounds of various structures. They can be used in making syntheicresins and polymers, dyes, medicinals, insecticides. m.

A feature of our invention is that we have provided fluorocarbonaldehydes and aldehydrols containing a plurality of carbon atoms in thefluorocarbon radical, as well as the first member of the series whichhas only a single fluorinated carbon atom. Compounds containing apolycarbon fluorocarbon chain attached to the carbonyl function arevaluable for making a variety of derivative compounds wherein thepresence of a polycarbon fluorocarbon chain is desirable, and which haveproperties not obtainable with a single fluorinated carbon atom.

A striking illustration of the effect or fluorocarbon chain length isprovided by a simple demonstration experiment. To a flask containingtoluene add 1% of n-heptatluoro'butyric acid, CF:(CF2):COOH, and shake.The toluene no longer wets the glass surface as it did initially, theangle of contact being changed from zero to almost This is because then-heptafluorobutyric acid molecules are adsorbed by the glass and forman interfacial film which the toluene does not wet. Trifluoroaceticacid, CFaCOOH, does not have this property and in fact tends to destroythe anti-wetting characteristic of the n-heptafluorobutyric acid whenpresent with it. This demonstrates that a single fully fluorinatedcarbon atom, bonded to a functional group, differs in important respectsfrom a fuly iluorinated polycarbon chain bonded to the same functionalgroup.

The solubility in water of the fluorocarbon aldehydrols decreases withincrease in length of the fluorocarbon chain. Th first two members ofthe series are soluble, the third member is sparingly soluble, and thehigher members are relatively insoluble in water. The first two membersthe higher members are solids. Aldehydrols containing ten or more carbonatoms become increasingly wax-like and water-repellent with increase influorocarbon chain length.

Our invention embraces compounds containing from two to eighteen carbonatoms in the molecule.

Trifluoroacetaldehyde, CFaCHO, has a boiling point of about minus C. at740 mm. This compound can also be designated by the name fluoraP (byanalogy to chloral and bromal), The aldehydrol form, CFsCH(OH) a, whichcan be termed fluoral hydrate, has a boiling point of about 105 C.

Pentafluoropropionaldehyde, CzFaCHO, has a boiling point of about 2 C.at 740 mm. The aldehydrol form. C2F5CH(OH)2, boils somewhat above 93 C.

n-Heptafluorobutyraldehyde, CaFwCHO, has a boiling point of about 28 C.at 740 mm., a density of 1.505 at C., and a refractive index of 1.273 at4 C. The aldehydrol form,

has a boiling point of about 93 C., and a melting point of about 61?. C.

n-Nonafluorovaleraldehyde, CiFQCHO, has a boiling point of about 48 C.at 740 mm. The aldehydrol form, CsFeCI-HOHM, has a boiling point ofabout 100 C. at 740 mm.

The recovery of the pure aldehydes is diflicult in the case of thehigher members of the series which have ten or more carbon atoms in themolecule (nine or more carbon atoms in the fluorocarbon radical). Thealdehydrol compound CnF1sCH(OH)a is a solid material having a meltingpoint of about 114 C. and a boiling point of about 148 C. at 740 mm.Data on the corresponding aldehyde is not given as we are not certainthat it was recovered in reasonably pure form, although identificationwas made by a positive Schifi test. As previously mentioned, thealdehydrol form can be used in the preparation of aldehyde derivativesand it is not essential, from a practical standpoint, that the aldehydebe prepared as such.

Examples of derivatives of our new compounds are the diacetates of thealdehydrols, which have the generic formula: RrCH(OAc)2. member of thisseries is CFaCH(OAc)2, a liquid having a boiling point of about 149 C.at '740 mm., a density of 1.291 at 20 C., and a refractive index of1.354 at 20 C. The compound CzFrCH OAc 2 has a boiling point of about164 C. at 740 mm., a density of 1.431 at 20 C., and a refractive indexof 1.338 at 20 C. These compounds are claimed in our copendingapplication S. N. 186,690, filed September 25, 1950.

Further examples of derivatives are the semicarbazones of the aldehydes.The compound C3F1C2NNHCONH2 has a melting point of about 52 C.

Further examples are the mono-substituted 2,4-dinitrophenylhydrazonederivatives of the aldehydes. The compound CF3CHINNHCeI-I3(NO2) a has amelting point of about 136 C. The compound CzF5CH:NNHCsHa(NOz)2 has amelting point of about 126 C. The compound CeFioCH I NNHCcHa (N02) 2 hasa melting point of about 128 C. I

A dl-substituted 2,4 dinitrophenylhydrazine The first 4. derivative ofan aldehydrol is illustrated by the compound C3F1CH NHNHCH3 NO2 1):,which has a melting point of about 99 C.

Further examples are the alcohols that can be formed by the Grignardreaction. Thus by subjecting heptafluorobutyraldehyde to the action ofmethyl magnesium iodide, the compound 1- heptafluoropropylethanol,CaF-zCH(CHa) OH, can

be obtained.

Method of making ,as sulfuric acid. phosphorous pentoxide, aceticanhydride, etc.

The following example illustrates the method as applied to the making ofheptafluorobutyrah dehydrol, C3F'ICH(OH)2 and heptafluorobutyraldehyde,CaF-zCHO, by reduction of heptafluorobutyric acid. CaF'zCOOH, viz.:

The reaction apparatus is a dry 3000 ml. 3- necked glass flask equippedwith a stirrer, a water-cooled reflux condenser, a dropping funnel, anda gas inlet tube so that dry nitrogen can be flowed through the system.The apparatus should be dried at C. before use, and assembled whilestill hot with dry oxygen-free nitrogen passing through the apparatus.

Precautions must be observed in using the LiAlHi reduction agent. It issensitive to 1120 and CO2 in the air, is spontaneously inflammable withwater, and inflames on rubbing un-j protected in a mortar. The materialis crushed in a mortar under a dry nitrogen atmosphere and added rapidlyto the ether in the flask withv a slow nitrogen stream flowing throughthe system. In case of a fire, do not use a water or carbon dioxide fireextinguisher. Use nitrogen or a dry-powder type of extinguisher. Withnitrogen flowing through the system, the flask is charged with 1250 ml.of dry diethyl ether and then with 19 grams (0.5 mol) of powderedLiAlI-Li. The suspension is stirred until the LiAlH4 dissolves, leavingonly a slight haze of insoluble impurities in suspension. To thissolution is added dropwise 107 grams (0.5 mol) of CaF'zCOOH in 1000 ml.of dry diethyl ether while the flask is kept cool in an ice bath. Theaddition is made at'a. rate which will produce a gentle reflux of theether. Upon completion of the addition the nitro gen is turned off andthe reaction mixture is stirred for 48 hours. Then the nitrogen isturned on, the flask is cooled with an ice-salt mixture, and suflicientwater is added dropwise to decom pose the excess LiAlHi. Hydrogen isevolved as long as the latter is present. The endpoint is not sharp, butabout 10 ml. water should be sufficient, and 2 to 5 mi. excess watershould be added to be sure all unreacted LiAlHi is destroyed. A modifiedprocedure is to make the first small addition of water by means ofdiethyl ether saturated with water, and use a 2 cubic ft. per hour sweepstream of nitrogen saturated with water vapor. To avoid explosions,great care -should be exercised to maintain a nitrogen atmosphere in thereaction flask.

7 After the addition of water is completed, add

immediately an ice-cold solution of 80 ml. (1.5 mols) of concentratedsulfuric acid in 200 ml. of water, with continued cooling. Separate thetwo layers and extract the bottom water layer three times with diethylether. The upper ether layer and the ether extracts from the bottomlayer are combined and the ether removed in a stripping still. A stillwith 4 to 6 theoretical plates is sufllcient.

The residue is dried over anhydrous calcium sulfate (Drierite) anddistilled through an efflcient semi-micro fractionating column, whichshould have 6 to theoretical plates. The cut boiling from 85 to 95 0.,which should weigh 85-95 grams, contains the fluorocarbon aldehydrolproduct.

The aldehyde can be prepared by charging-the above-mentioned 85-95 cutinto a 2-neck 200 ml. flask equipped with a dropping funnel and a drysemi-micro fractionating column. Care should be taken that all jointsare tight. 35 ml. of concentrated sulfuric acid is added slowly throughthe dropping funnel and the resulting mixture is refluxed gently tocause decomposition of the aldehydrol compound, which is the precursorof the aldehyde. The mixture is gently refluxed as too much heat maycause a sudden evolution of aldehyde. The aldehyde product distils outat a temperature of 28-30 C. It is collected in a receiver cooled bysolid-CO2, whose outlet is protected by a trap cooled by solid-CO2 and adrying tube. The yield is about 40%.

The fluorocarbon aldehyde product is kept dry and cold (below 0 C.) forstorage.

The products made by this exemplary procedure, namely, C3F1CH(OH)2 andCaF'zCHO, have been previously characterized by their physical andchemical properties, together with those of other members of the series.The CaFvCHO product had a determined molecular weight of 196 (calculatedfrom vapor density) in substantial agreement with the formula weight of198. The infra-red spectrum contained the $0 band and also showed thepresence of C-F and C-H bonds. The corresponding aldehydrol,

was analyzed for fluorine and a value of 60.5% F was obtained. The valuecalculated from the formula is 6.6% F.

Preparation of fluorocarbon acids The fluorocarbon monocarboxylic acidsutilized as starting compounds in the foregoing method of making ournovel compounds, have the generic formula CnF2n+ lCOOH.

These fully fluorinated acids are extremely strong, the acid strength ofaqueous solutions being of the same order of magnitude as that of strongmineral acids, whereas the corresponding hydrocarbon acids arerelatively weak. They can be made by hydrolyzing the corresponding acidfluorides (RrCOF), which are highly reactive and readily react withwater to form the carboxylic acid derivatives. The acid fluorides can bemade by electrolyzing a solution of anhydrous liquid hydrogen fluoridecontaining a dissolved hydrocarbon monocarboxylic acid (or itsanhydride) of corresponding carbon skeletal structure,

' by passing direct current through the solution at a cell voltage whichis insufficient to generate molecular (free elemental) fluorine underthe existing conditions, but which is sufficient to cause the formationof the fully fluorinated acid fluoride (RrCOF) ata useful rate.

Excellent results can be obtained with simple single compartmentelectrolytic cell arrangements. No diaphragm is needed betweenelectrodes. The cell can be readily operated at atmospheric pressure,employing a cell temperature in the neighborhood of 0 C. The cell andthe cathodes can be made of iron or steel, and the anodes of nickel, andsuch cells have been satisfactorily operated at approximately 5 to 6volts, D. C. The fluorocarbon acid fluoride product of the celloperation is relatively insoluble in the electrolyte solution and eithersettles to the bottom of the cell from which it can be drained withother fluorocarbon products of the process, or is volatilized andevolves from the cell in admixture with the hydrogen and other gaseousproducts. The fluorocarbon acid fluoride compound can be hydrolyzed tothe fluorocarbon acid derivative (RrCOOH) while still mixed with otherproducts and the acid product can be separated and recovered. Anotherprocedure is to react the acid fluoride with ammonia to produce theamide (RrC0NH2), a solid compound which can be readily separated andpurified, and then bydrolyze the latter to produce the fluorocarbon acid(RrCOOH).

The electrochemical process is described and claimed in the copendingapplication of J. H. Simons, S. N. 62,496, filed November 29, 1948,since issued as Patent No. 2,519,983 on August 22, 1950. Fluorocarbonacids are described and claimed in the copending application of A. H.Diesslin, E. A. Kauck and J. H. Simons, S. N. 70,154, filed January 10,1949, which also describes the electrochemical process.

What we claim is as follows:

1. As new compositions of matter, the noncyclic reactive fluorocarboncompounds of the class consisting of the fluorocarbon aldehydes havingthe formula CnF2n-l-ICHO and the corresponding fluorocarbon aldehydrolshaving the formula cnF2n+1CH(OH)2, said compounds having from 2 to 18carbon atoms in the molecule.

2. The compound trifluoroacetaldehydrol having the formula CF3CH( OH) 2.

3. The compound pentafiuoropropionaldehydrol having the formulaC2F5CH(OH):2.

4. The compound heptafluorobutyraldehydrol having the formula C3F7CH(OH)z.

5. The compound trifluoroacetaldehyde having the formula CFaCHO.

6. The compound heptafluorobutyraldehyde having the formula CaFwCHO.

7. As new compositions of matter, the noncyclic reactive fluorocarboncompounds of the class consisting of the fluorocarbon aldehydes havingthe formula CnFZnHCHO and the corresponding fluorocarbon aldehydrolshaving the formula cnF2n-i-lCH(OH)2, said compounds having from 3 to 18carbon atoms in the molecule.

I DONALD R. HUSTED.

ARTHUR H. AHLBRECHT.

REFERENCES CITED The following references are of record in the Hackh:Chemical Dictionary, 3rd edition, 1944, f pages 143, 191 and 444. TheBlakiston Company.

Henne et al.: Jour. Am. Chem. $00., vol. 70, pages 1968, May 1948.

Groog et al.: '71 JACS, 1710-11 (May 1949).

1. AS NEW COMPOSITIONS OF MATTER, THE NONCYCLIC REACTIVE FLUOROCARBONCOMPOUNDS OF THE CLASS CONSISTING OF THE FLUOROCARBON ALDEHYDES HAVINGTHE FORMULA CNF2+1CHO AND THE CORRESPONDING FLUOROCARBON ALDEHYDROLSHAVING THE FORMULA CNF2N+1CH(OH)2, SAID COMPOUNDS HAVING FROM 2 TO 18CARBON ATOMS IN THE MOLECULE.